Electronic indicator tube having primary characters and auxiliary characters



T. C. MALONEY Sept. 9, 1969 ELECTRONIC INDICATOR TUBE HAVING PRIMARY CHARACTERS AND AUXILIARY CHARACTERS Filed Sept 25, 1967 Y INVENTO R. THOMAS c. MALONEY B ATTORNEY United States Patent 015cc 3,466,486 Patented Sept. 9, 1969 3,466,486 ELECTRONIC INDICATOR TUBE HAVING PRIMARY CHARACTERS AND AUXILIARY CHARACTERS Thomas C. Maloney, Bernardsville, N.J., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Sept. 25, 1967, Ser. No. 671,540 Int. Cl. H01j 7/42 US. Cl. 313109.5 9 Claims ABSTRACT OF THE DISCLOSURE Background of the invention Many types of indicator tubes known as Nixie tubes have been made and sold by Burroughs Corporation for many years. Generally, these tubes include a stack of ten cathode electrode numerals mounted parallel to each other facing a viewing window in the tube envelope. These tubes have also been made with cathodes in the form of letters and various mathematical symbols. However, until relatively recently, the tubes have not included decimal points. But a need for decimal points has now arisen, and the prior art provides no satisfactory teaching as to how to build a multi-cathode indicator tube which also includes one or more decimal point cathodes. The present invention concerns the provision of such a tube.

Summary of the invention Briefly, an indicator tube employing the invention includes an electrode assembly comprising a stack of cathode electrodes enclosed within a generally tubular anode electrode. The assembly also includes a decimal point arrangement mounted on tube pins and positioned within the tubular anode on either side of the stack of cathode electrodes.

Description of the drawing In the drawing:

FIG. 1 is a perspective view of a tube embodying the invention;

FIG. 2 is an enlarged, front elevational view of a decimal point construction used in the tube of the invention; and

FIG. 3 is a side elevational view of the structure shown in FIG. 2.

Description of the preferred embodiment For purposes of illustrating the invention, a side-view indicator tube 10 is shown. In such a tube, the glow cathodes are viewed through the side wall of the tube envelope. However, the universality of the principles of the invention will be clear to those skilled in the art.

Referring to the drawing, indicator tube 10 embodying the invention includes an envelope which contains a gas suitable for supporting a cathode glow. Such a gas may be argon, neon, or the like, at a pressure which may be readily determined by those skilled in the art. The envelope 20 is generally elongated and its side wall 22 comprises a viewing window. The envelope includes a base or stem 24 through which metal pins 25 extend and to which cathode electrodes 26 are connected by leads 27. The usual tubulation 28 is provided in the dome of the envelope as shown, or it may be in the stem 24.

The electrode assembly mounted inside the envelope 20 includes a lower insulating disk or plate 34 of mica or the like seated on the upper ends of glass sleeves 35 which are fitted on a plurality of tube pins including at least two pins 25 and longer pins 31 and 32 at the front of the tube. The pins 31 and 32 extend through suitable apertures 136 in the mica disk. Glass sleeves 35 elevate plate 34 above pins 25. The mica plate 34 also includes either a central slot 40 or comparable individual apertures through which the cathode leads 27 extend from the cathode electrodes 26 to tube pins 25. Seating of lower mica plate 34 on the glass sleeves 35 so that it is spaced above pins 25 facilitates the arrangement of the cathode leads 27.

The electrode assembly of tube 10 includes an anode structure which comprises a solid rear plate 50 and a front mesh screen 58 which faces the viewing window 22 of the tube. The back plate and front screen are curved so that they meet and form a generally hollow tubular chamber in which the cathode electrodes 26 are positioned. The plate and screen are seated on the bottom mica plate 34 and are secured to it and to an upper mica plate 64 by means of the usual tabs (not shown). The rear anode plate 50 is also welded to two tube pins 25 (not shown) for rigidity and to provide means for connecting anode potential thereto. Preferably, glass sleeves 35 would be provided on these pins to shield them from adjacent pins which carry cathode potential to minimize spurious cathode glow.

A pair of cathode support posts including an upper support post and a lower support post 84 are secured between the front screen and rear anode plate. The posts 80 and 84 are either made of an insulating material such as a ceramic, or they are made of metal and coated with glass or the like to provide the required insulation from the cathode electrodes mounted thereon. The support posts 80 and 84 are secured to the anode screen and plate by welding or by means of eyelets crimped to the ends of the posts.

The electrode assembly also includes a plurality of metal cathode electrodes 26 which are in the form of characters, usually numerals O to 9. To simplify the drawing, fewer than ten cathodes are shown. In addition, arrangements for insulatingly mounting the cathodes on posts 80 and 84 are well known and are not described in detail.

The tube 10 also includes two decimal point arrangements positioned adjacent to the lower ends of the cathodes on the left and right sides thereof on pins 31 and 32, inside screen 58, and suitably positioned to provide the desired representation. In the decimal point constructions, the outer diameter of the glass tubes 35 is greater than the diameter of the apertures 136 in the mica disk 34 through which the pins 31 and 32 extend. An insulating washer 160 of glass or ceramic is threaded on each pin 31 and 32 and is seated on the upper end of the glass tube within each aperture 136 in the mica disk. A metal cathode disk 150, which operates as the decimal point, is welded to the upper end of each pin 31 and 32. The cathode disks may be positioned on pins 31 and 32 so that they either seat on the ceramic disk 160, or so that they are raised slightly above them. The decimal point cathode disks 150 also preferably have a diameter slightly smaller than the diameter of the apertures 136 in the mica disk 34 so that, when the tube 10 is assembled, the decimal disks 150, glass tubes 35, and ceramic disks can be mounted on the stem 24, and then this assembly can be inserted into the mica disk 34 which itself might already carry all of the other tube components.

The combination of glass tubes 35 and ceramic disks 160 have been found to prevent the spread of sputtered cathode material from the decimal point disks 150 to other parts of the tube and particularly down the lengths of pins 31 and 32.

For optimum operation and long life, the tube 10 includes in its atmosphere a small quantity of mercury vapor which serves to minimize cathode sputtering during tube operation. The mercury may be provided in any suitable fashion. For example, it may be introduced directly with the tube gas or gases, or, in a preferred arrangement, it is provided in a glass capsule 168 which is surrounded by a coil of heating wire 170 connected between two pins 25. Heating of the wire by current flow causes the mercury to expand and fracture the capsule, whereby the mercury vapor escapes into the tube atmosphere.

The indicator tube of the invention has many advantages, the most important of which is that it provides an optimum integration of ten cathode electrodes and auxiliary, remotely located symbols such as decimal points, in a compact assembly suitable for mass production.

What is claimed is:

1. A cathode glow indicator tube including:

an envelope filled with a gas for supporting cathode glow and including a viewing window and a stem which carries a plurality of tube pins,

a lower mica disk supported adjacent to said stern and an upper mica disk spaced above said lower mica disk,

a cylindrical anode electrode means positioned between said lower and upper mica disks,

said anode means including a solid rear plate and a front screen,

said anode rear plate being mechanically and electrically connected to at least one of said tube pins,

21 pair of support posts secured between said rear plate and front screen,

a plurality of cathode electrodes supported between said support posts facing said viewing window,

a decimal point assembly on either side of said stack of cathodes and near the lower ends thereof, each decimal point assembly including a tube pin extending upwardly through an aperture in said lower mica disk, a glass sleeve on each tube pin between said lower mica disk and said stem with said mica disk seated on said glass sleeve, an insulating washer threaded on the tube pin and seated on said glass sleeve in said aperture, and a metal disk cathode secured to the upper end of the pin with its periphery adjacent to said washer.

2. The tube defined in claim 1 wherein each decimal point disk cathode rests on the surface of the insulating washer beneath it.

3. The tube defined in claim 1 wherein each decimal point disk has a diameter smaller than the diameter of the aperture in the mica disk through which the tube pin on which it is mounted extends.

4. The tube defined in claim 1 wherein said decimal point assembly, said tube mounting pin therefor extends from said stem and through an aperture in said lower mica disk to the height at which the decimal point disk is to be positioned, a glass tube enclosing the portion of said mounting pin between said stem and said lower mica disk and having its upper end positioned adjacent to said lower mica disk, said glass tube having a larger outside diameter than said aperture in said lower mica disk, 21 cermic annulus threaded on said mounting pin and seated within said aperture on the upper end of said glass tube, said ceramic annulus having an outside diameter almost as large as that of said aperture, and the diameter of said metallic decimal point disk is smaller than that of said aperture.

5. An indicator tube comprising:

a gas-filled envelope including a stern which carries a plurality of tube pins,

a stack of cathode electrodes and an anode electrode mounted in said envelope and facing a portion of said envelope as a viewing window,

an insulating electrode support disk positioned adjacent to the stem of the envelope at the lower end of said stack of cathode electrodes,

an auxiliary indicator electrode assembly positioned in operative relation with said stack of cathode electrodes at the lower end thereof,

said auxiliary electrode assembly including an insulating washer supported in an aperture in said insulating disk and an auxiliary indicator electrode seated on said washer and secured to one of said tube pins which extends from said auxiliary electrode through said aperture in said insulating disk to said stem.

6. The tube defined in claim 5 wherein said auxiliary electrode is smaller than said aperture and can fit through said aperture during tube assembly.

7. The tube defined in claim 5 and including an insulating tube enclosing said one of said tube pins and positioned between said support disk and said stem and supporting said insulating washer on its upper end.

8. The tube defined in claim 5 wherein said auxiliary electrode comprises a disk operable as a decimal point and secured to said one tube pin with its periphery contiguous to said washer.

9. The tube difined in claim 5 wherein said auxiliary electrode is oriented in a vetrical plane facing said viewing window and having its periphery touching said washer.

References Cited UNITED STATES PATENTS 3,250,938 5/1966 Frouws et al. 31310 9.5 3,358,176 12/1967 Rosenberg et al. 313-109.5

JAMES W. LAWRENCE, Primary Examiner DAVlD OREILLY, Assistant Examiner U.S. Cl. X.R. 3 13251 

